Forum Index
shamskm.com Home
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

How far is the Andromeda Galaxy?

 
Post new topic   Reply to topic     Forum Index -> Science
View previous topic :: View next topic  
Author Message
Admin
Site Admin


Joined: 25 Sep 2007
Posts: 268

PostPosted: Sun Nov 22, 2009 12:21 am    Post subject: How far is the Andromeda Galaxy? Reply with quote

The Andromeda Galaxy, also known as M31, is the nearest neighbour of our Milky Way Galaxy. But how far is our ‘nearest neighbour’ from Earth.

It’s a distance of 2.5 million light years. One light year is the distance travelled by light in a vacuum in one year. That means in one light year, light travels a distance of about 9,460,730,472,580.8 km (or 9.461 * 10^12 km).

In one million light years, light travels 9.461 * 10^18 km (here ‘^’ means to the power, hence 10 to the power 18 ).

So in 2.5 million light years, light travels a distance of 2.365 * 10^19 km.

Now if you send an email to a friend in Andromeda Galaxy, that travels with the speed of light, then it will need 2.5 million years to reach there. And your friend’s reply will take another 2.5 million years to reach you. So it’s a business of about 5 million years. Not baaad Smile.

Although, M31 is so far, but it can be visible in naked eyes as a faint mark. That means the image we see is the ‘past’ of M31. Because light needed 2.5 million years to reach Earth from the Andromeda Galaxy. How it exactly looks today, we will know it after 2.5 million years.



Image: Great Andromeda Nebula. Published in 1899. Author: Isaac Roberts.
Source:A Selection of Photographs of Stars, Star-clusters and Nebulae, Volume II, The Universal Press, London, 1899.

So looking up to the Heaven we see not only our present day ‘Moon’ and ‘Sun’, but at the same time we see the ‘past’ of another celestial body (i.e. we are looking at the past from the present). That’s amazing.

Sources: International Astronomical Union (IAU), Wikipedia.

P.S. You can use Wolframalphato calculate these numbers.
Back to top
View user's profile Send private message Send e-mail
Display posts from previous:   
Post new topic   Reply to topic     Forum Index -> Science All times are GMT + 2 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group